The present invention relates to an oral composition effective for remineralizing teeth, and a method for using the same.
In an oral cavity, there is an equilibrium state in which a constituent ingredient of teeth, hydroxy apatite, dissolves from the teeth, and a calcium ion or a phosphate ion in a saliva deposits onto the tooth surface. Due to this equilibrium state, the tooth surface is always changing. When the equilibrium moves towards the dissolution of hydroxy apatite, a white spot develops on the tooth surface, which leads to a caries-inducing state referred to as demineralization. When the equilibrium moves towards the reformation of a demineralized enamel from hydroxy apatite, which is referred to as remineralization, caries can be prevented or treated by the remineralization.
A major factor governing the equilibrium is a saturation degree of hydroxy apatite in the oral cavity. That is, when hydroxy apatite becomes supersaturated, the remineralization occurs. Reversely, when the saturation degree of hydroxy apatite is lowered, the demineralization occurs. Since hydroxy apatite dissolves in an acid, in an acidic region, the saturation degree is lowered and the demineralization occurs.
Thus, there has been proposed an oral composition into which hydroxy apatite and calcium compounds, constituent ingredients thereof are blended and which promotes the remineralization.
For example, there is described that the remineralization is promoted by using certain hydroxy apatite in JP-A 55-57514, tetra-calcium phosphate in JP-A 1-71807, or amorphous calcium phosphate in U.S. Pat. No. 5,562,895. There is described a composition with added soluble calcium phosphate containing calcium and phosphate in the ionized state in JP-A 8-319224, and there is described a toothpaste containing silica and dicalcium phosphate in JP-A 8-502988 (WO 94/10969).
For the remineralization, it is also known that fluoride ion-feeding compounds release a fluoride ion to promote a remineralization process and, thereby, reduce caries that has previously been existed within a tooth structure. For example, there are proposed a combination of xylitol and a fluoride in U.S. Pat. No. 371,145, and a combination of hydroxy apatite and a fluoride in JP-A 1-110608. However, although a certain effect has been recognized for the primary teeth, a product which can be said to be sufficient for remineralizing the second teeth has not been developed yet.
By the way, it has been hitherto known that a fluoride ion reinforces a dentine. Thus, an attempt to enhance the caries preventing effect has been tried by intensifying such an action of a fluoride ion. In JP-A 63-246316, pyridoxine derivatives are blended into an oral composition for the purpose of promoting uptake of a fluoride ion and improving an acid-resistant property of the teeth. There is proposed a poly-cationic polymer in JP-A 3-5417. However, none of them disclose the remineralizing action.
The previous methods, which employ a composition into which hydroxy apatite is blended or an oral composition into which a fluoride is blended, can not accomplish the desired effect on the teeth under an oral cavity environment where the teeth are easily demineralized, or on the teeth which has already begun to be demineralized. Also, there is a limitation that a pH of a formulation as an oral composition is required to adjust to a higher pH than that of a weak acid because when the oral cavity is made acidic, the demineralization is caused.
An object of the present invention is to enhance the effects of preventing or treating caries of an enamel or root surface, or dentin hyperesthesia, by promoting the ability of fluorine to remineralize.
The present inventors extensively studied the promotion of the remineralizing action of a fluoride ion and, as a result, found that polyvinyl acetal diethylaminoacetate has an excellent remineralizing action promoting effect. Polyvinyl acetal diethylaminoacetate was developed as a coating agent for tablets, and, for instance, there is reported in JP-A 5-339136 that it is effective for suppressing dental plaque accumulation or promoting adsorption of a fluoride onto the tooth surface. However, its remineralizing action promoting effect is not known.
Also, the present inventors found that even when a pH of an oral composition is adjusted to an acidic region of about 3-6.5, the demineralization is not caused, and, unexpectedly, the remineralizing action promoting effect is remarkably improved than in a neutral region. Moreover, the present inventors found that the remineralizing action promoting effect is also improved by blending an anionic surfactant therein.
The present invention was completed based on such novel findings and in one aspect thereof, provides a method of remineralizing teeth which comprises using an oral composition comprising polyvinyl acetal diethylaminoacetate and a fluoride ion-feeding compound which feeds a fluoride ion. This oral composition may further contain an anionic surfactant.
In an another aspect, the present invention provides an oral composition for remineralizing the teeth, which is used for the method of the present invention.
Polyvinyl acetal diethylaminoacetate to be used in the present invention is an acetal produced by dehydration between polyvinyl alcohol and acetaldehyde, and which is a basic high-molecular compound in which a part of the remaining hydroxyl groups are bound to diethylaminoacetic acid via an ester linkage and, for example, a commercially available product such as xe2x80x9cAEAxe2x80x9d (Sankyo Corporation) may be used.
An amount of polyvinyl acetal diethylaminoacetate to be blended is in the range of 0.01-10% by weight, preferably in the range of 0.02-2% by weight, from a viewpoint of the promotion of the remineralizing action.
As the fluoride ion-feeding compound which feeds a fluoride ion, there are sodium fluoride, potassium fluoride, ammonium fluoride, calcium fluoride, copper fluoride, zinc fluoride, lithium fluoride, cesium fluoride, zirconium fluoride, tin fluoride, sodium monofluorophosphate, potassium monofluoro-phosphate, sodium titanium fluoride, potassium titanium fluoride, hexylamine hydrofluoride, laurylamine hydrofluoride, cetylamine hydrofluoride, lysine hydrofluoride, glycine hydrofluoride, alanine hydrofluoride, fluorosilane and the like, and they can be used alone or in a combination of two or more of them. In view of the oral use, preferred are sodium fluoride, potassium fluoride, ammonium fluoride, tin fluoride, sodium monofluorophosphate, and potassium monofluorophosphate. An amount of the fluoride ion-feeding compound to be blended is in the range of 10-50,000 ppm, preferably 90-20,000 ppm in terms of a fluoride ion based on the total amount of the oral composition, from a viewpoint of the remineralizing effect. When the amount is below 10 ppm, the remineralizing action can not be expected and, when it exceeds 50,000 ppm, the remineralization promoting effect by polyvinyl acetal diethylaminoacetate does not increase much, being not economical. In a method of using almost every day for a long period of time, the concentration in the composition of 90-5,000 ppm is particularly preferred and, in a method of using at long-term intervals exceeding one month, 9,000-20,000 ppm is particularly preferred.
As the anionic surfactant to be used in the present invention, there are salts of N-long chain acyl basic amino acid such as sodium salt of N-acyl-L-glutamate, sodium salt of N-hydrogenated tallow fatty acid acyl-L-glutamate, sodium lauroyl sarcosinate, water-soluble salts of higher alkyl sulfate having alkyl group of 8-18 carbon atoms such as sodium lauryl sulfate and sodium myristyl sulfate, polyoxyethylene alkyl sulfate salt, alkylsulfoacetate salt, xcex1-olefin sulfonate salt, sulfosuccinate derivatives, sodium salt of higher fatty acid monoglyceride monosulfate, N-methyl-N-palmitoyltauride salts and the like. An amount of the anionic surfactant to be blended is 0.01-10% by weight, preferably 0.1-5% by weight based on the total amount of the oral composition.
As an acid to be used for adjusting a pH of the oral composition, citric acid, malic acid, phosphoric acid, and aromatic carboxylic acids such as benzoic acid, nicotinic acid and salicylic acid, and salts thereof are exemplified, and one or more selected from them may be used. A preferred pH range is 3-6.5. When a pH is below 3, the demineralization by an acid is remarkable and, when a pH exceeds 6.5, the effect becomes weak. An amount of the acid to be blended is preferably 0.01-3% by weight and, when it exceeds 3% by weight, a physical property as an oral composition becomes unstable.
The oral composition of the present invention may be appropriately formulated, depending upon its use, into a form such as toothpaste, pasta, powder or liquid dentifrice, wetting dentifrice, gel, cream, mouthwash, spray, foam, coating agent and the like, according to the conventional methods. Other ingredients to be blended are not particularly limited and the known polishing agents, humectants, thickening agents, foaming agents, preservatives, flavoring agents, therapeutic agents and the like may be blended into the oral composition, so long as they do not deteriorate the effects of the present invention.
A container may be made of compatible materials, all kinds of dispenser-container are usable, and a laminate tube made of aluminium or plastics, a plastic container such as of squeeze-type and pump dispenser, or an aerosol container may be used. In the case of a gel or varnish form, the composition may be contained in a syringe.
The method of the present invention may be practiced by applying the oral composition to the demineralized portion of the tooth such as by brushing or mouth washing. For example, in the case of a dentifrice or a mouthwash, they are used one to three times a day according to the conventional using method. Usually, 0.2-1.5 g of a dentifrice or 5-20 ml of a mouthwash as a daily amount is used so that the daily amount of a fluoride is 0.1-2 mg, particularly preferably approximately 1 mg. Moreover, the oral composition of the present invention may be formulated into the form such as a gel or a varnish to specifically apply onto the demineralized portion of the teeth in a topical manner. In the case of a gel or a varnish for the topical application, it may be applied in the frequency of once a month to once a year.
The remineralization of teeth is accomplished by the above way of using and, thereby, the effects of preventing or treating caries, root surface caries and dentin hyperesthesia can be exerted.